10S MOEPHOLOGY AND EVOLUTION
canine tooth. And slight ridges are produced by the fangs of the premolar and molar teeth. A well-marked suture exists between the maxilla and premaxilla.
JTorma Lateralis.—The alisphenoid (great wing of the sphenoid) meets the parietal bone in the pterion. The zygomatic arch is slender, and conceals the slightly recurved tip of the coronoid process of the mandible. When traced backwards it is continued upwards above the circular aperture of the long, bony external auditory meatus. No mastoid process exists. The spheno-maxillary fissure is wide.
When the mandible is removed it is seen how it moves in a shallow glenoid fossa, but the ridge-like post-glenoid processes are well marked, and form some of the most lateral parts of the basis cranii or norma basalis.
The anterior part of the basis cranii is formed by the long, comparatively narrow hard palate with its bounding dental arcade. ,Well-marked sutures divide the palate into three parts. Most anteriorly lie the premaxillae bearing the incisor teeth; and the sutures marking them off from the maxillae are continuous with the posterior borders of the large anterior palatine foramina, which transmit palatine vessels and nerves. The middle part is formed by the palatal processes of the maxillae; and the posterior part, which is formed by the palate bones, is terminated in the middle line by a very small posterior nasal spine. Sometimes the spine is absent. The posterior palatine foramina are entirely on the palate bones, but they may be concealed by small bony shelves. The entire bony palate is curved from side to side. The horizontal plates of the